U.S. patent number 4,867,012 [Application Number 07/198,139] was granted by the patent office on 1989-09-19 for variable speed transmission.
Invention is credited to Clifford B. McGarraugh.
United States Patent |
4,867,012 |
McGarraugh |
September 19, 1989 |
Variable speed transmission
Abstract
Differential-gearing devices are disclosed in which the
differential pinion gears are controlled to induce a speed
difference between output shafts, provide a locking and limited
slip differential to equalize the speeds of the output shafts or
limit their speed difference, provide a clutch for controlling the
coupling and uncoupling of an input shaft to an output shaft, and
provide a variable speed transmission. These operational modes are
implemented by mounting hydraulic motor or pump units on the
rotating carrier of the differential apparatus, the pinion gears
being fixed to the shafts of the respective units. A controllable
external fluid source independent of the carrier is in fluid
communication with the units via conduits through the stationary
housing of the differential device and the rotating carrier. Fluid
flow may be either blocked, limited or unimpeded between the source
and the units to effect the desired control of the pinion gears to,
in turn, determine the operational mode of the apparatus.
Inventors: |
McGarraugh; Clifford B.
(Perryton, TX) |
Family
ID: |
26728230 |
Appl.
No.: |
07/198,139 |
Filed: |
May 24, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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50402 |
May 18, 1987 |
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Current U.S.
Class: |
475/72; 475/74;
475/106; 475/23; 475/90 |
Current CPC
Class: |
F16H
3/72 (20130101) |
Current International
Class: |
F16H
3/44 (20060101); F16H 3/72 (20060101); F16H
003/44 () |
Field of
Search: |
;74/773,774,776 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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550884 |
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Mar 1923 |
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FR |
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925084 |
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Aug 1947 |
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FR |
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116846 |
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Feb 1918 |
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GB |
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Primary Examiner: Diehl; Dwight G.
Attorney, Agent or Firm: Chase; D. A. N. Herman; Joan O.
Parent Case Text
This application is a division, of application Ser. No. 050,402,
filed 5/18/87 now abandoned.
Claims
Having thus described the invention, what is claimed as new and
desired to be secured by Letters Patent is:
1. In a variable speed transmission apparatus:
a rotatable carrier;
a pinion gear;
a fluid pump unit carried by said carrier and having a rotatable
operating shaft to which said pinion gear is fixed, and further
having fluid inlet and outlet means;
a pair of rotatable, input and output shafts having inner ends
provided with gear means engaging said pinion gear;
controllable, variable displacement fluid motor means independent
of said carrier and connected with said output shaft; and
means communicating said fluid inlet and outlet means of the pump
unit with said motor means, whereby the fluid displaced by said
motor means determines the speed difference between the input and
output shafts.
2. The apparatus as claimed in claim 1, wherein said fluid motor
means includes a piston-type motor unit and means for changing the
length of the stroke of the pistons to vary the displacement
thereof.
3. The apparatus as claimed in claim 1, wherein said fluid motor
means includes a hydraulic motor provided with pistons having
strokes of variable length.
4. The apparatus as claimed in claim 1, wherein said means mounting
said carrier includes a housing that is stationary with respect to
the rotatable carrier, and wherein said communicating means
includes conduit means extending through said housing to said
carrier therein and having means presenting continuous fluid
connections to said rotatable carrier through said stationary
housing.
5. In a variable speed transmission apparatus:
a rotatable carrier;
a pair of opposed pinion gears;
a pair of fluid pump units carried by said carrier and each having
a rotatable operating shaft to which a corresponding pinion gear is
fixed, and further having fluid inlet and outlet means;
a pair of rotatable, input and output shafts having inner ends
provided with gear means engaging said pinion gears;
controllable, variable displacement fluid motor means independent
of said carrier and connected with said output shaft; and
means communicating said fluid inlet and outlet means of the pump
units with said motor means, whereby the fluid displaced by said
motor means determines the speed difference between the input and
output shafts.
Description
This invention relates to the utilization of differential gearing
for controlling power transmission in accordance with functions or
conditions desired by the operator and, in particular, to a
differential-gearing arrangement in which the pinion gears are
controlled in a manner to achieve the desired transmission of
rotating motion from input to output.
The construction and operation of differentials in vehicle drive
trains are well known. In a simple differential two driven ground
wheels or tracks are permitted to turn at different speeds in
response to unequal loads such as would occur, for example, when
the vehicle deviates from a straight course. Independent rotation
of the two wheel axles is achieved by the utilization in the
differential assembly of freely rotatable pinion gears in mesh with
side gears on the wheel axles, the shafts of the pinion gears being
mounted in a rotating differential case or carrier which is driven
by the propeller shaft that extends, typically, from the
transmission. When the output loads are matched, the differential
pinion gears are stationary on their axes but rotate with the
carrier to drive the two output axles at equal speeds. As the
vehicle traverses a turn, the pinion gears spin on their shafts
thereby transmitting more rotary motion to one axle than to the
other.
In the foregoing example of a simple differential, the pinion gears
permit a speed difference in response to the effect of an external
load or condition on the traction wheels, such as when a vehicle
turns or encounters an inconsistent road surface. In contrast to
this conventional usage of the differential principle as a means of
responding to load imbalances, in the present invention the pinion
gears are advantageously controlled to induce a speed difference,
lock the output axles to the input shaft as desired to force the
output axles to turn at the same speed, control the coupling and
uncoupling of input and output shafts, and provide a controllable
speed difference between input and output shafts.
It is, therefore, the primary object of the present invention to
provide a differential-gearing device in which the rotation of the
differential pinion gears is controlled in order to effect a
desired relationship between the rotatably driven input shaft and
the output shaft or shafts of the device.
A specific object of the present invention is to provide a device
as aforesaid in which the pinion gears are driven in either
direction of rotation by motor means on the carrier or differential
case, controlled by a power source which does not rotate with the
carrier and which enables the operator to control the speed and
direction of drive of the pinion gears to induce a corresponding
speed difference in the output shafts of the device.
Another specific object of the invention is to provide, in a second
embodiment of the aforesaid device, a locking and limited slip
differential in which fluid pump units on the carrier have
operating shafts to which the respective pinion gears are fixed,
and wherein by control of a fluid source for the pump units the
lock, limited slip and conventional differential operational modes
are achieved.
Still another specific object of the present invention is to
provide, in a third embodiment thereof, a clutch apparatus by which
input and output shafts may be selectively intercoupled and
uncoupled through the use of fluid pump units on the carrier driven
by the pinion gears and externally controlled to either permit free
rotation of the pinion gears or lock the same against rotation to
respectively isolate the input from the output or cause rotating
motion to be transmitted to the output shaft.
A further specific object of this invention is to provide, in a
fourth embodiment thereof, a variable speed transmission in which
the pinion gears of the differential apparatus are controlled by
pump units on the carrier and variable displacement fluid motor
means on the output shaft of the apparatus in order to impart a
desired speed difference between the input and output shafts.
Other objects of this invention will become apparent as the
detailed specification proceeds.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified, diagrammatic, cross-sectional view of a
differential device of the present invention employing hydraulic
motors on the carrier to control the speed and direction of drive
of the pinion gears to, in turn, induce a corresponding speed
difference in the output shafts.
FIG. 2 is a view similar to FIG. 1 but showing a second embodiment
of the present invention in which the controlled pinions provide a
locking and limited slip differential through the use of hydraulic
pump units on the carrier connected with the pinion gears.
FIG. 3 is a view similar to FIG. 1 but showing a third embodiment
of the present invention in which the aligned shafts coaxial with
the carrier provide the input to and the output from the device,
the arrangement in this embodiment providing a hydraulic clutch for
controlling the transmission of rotating motion from the input
shaft to the output shaft.
FIG. 4 is a view similar to FIG. 3 but showing a fourth embodiment
of the present invention in which the differential device provides
a variable speed transmission.
DETAILED DESCRIPTION
Referring to FIG. 1, a housing 10 contains a differential case or
carrier 12 supported therein on bearings 14 and 16 carried by
opposed, internally projecting, hollow boss portions 18 and 20
respectively of the housing 10. The carrier 12 is rotatable about
an axis that is coaxial with respect to left and right output
shafts or axles 22 and 24 which extend from housing 10 and are
journaled in bearings 26 in the wall of the housing and bearings 28
in the carrier 12. The inner ends of the output shafts 22 and 24
are closely spaced from each other and terminate at a central
chamber 30 within the carrier 12, and are provided with bevel side
gears 32 and 34, respectively, in mesh with a pair of opposed,
differential pinion gears 36 and 38.
An input shaft 40 forming, for example, part of the power train of
a vehicle extends, typically, from the vehicle transmission and
into the housing 10 through a bearing 42, the end of the input
shaft 40 being provided with a drive pinion 44 in mesh with a ring
gear 46 fixed to the carrier 12 and coaxial with the opposed output
shafts 22 and 24. Accordingly, the components thus far described
comprise a conventional bevel-gear differential for transmitting
and distributing the rotating motion of the input shaft 40 to the
two output shafts 22 and 24.
In the present invention, however, the pinion gear 36 is fixed to
the end of the drive shaft 48 of a hydraulic motor 50 mounted in
the wall of the carrier 12 and rotable therewith. As may be
appreciated from viewing FIG. 1, the wall of the carrier 12
surrounding the chamber 30 is suitably bored or recessed to receive
and retain the hydraulic motor 50. The fluid inlet and outlet 52,
54 of the hydraulic motor 50 are communicated by channels 56, 58
within the carrier body to corresponding ports 60, 62 on the
circumferential periphery of a reduced, cylindrical end portion 64
of carrier 12 that is received within the boss 20 and supported by
bearing 16. Three axially-spaced, annular seals 66 are sandwiched
between the outer, circumferential surface of end portion 64 and
the opposing inner surface of boss 20 and disposed, as seen in FIG.
1, between and on both sides of the ports 60 and 62. For example,
O-rings seated in grooves (not shown) in the boss 20 may be
employed as the seals 66. Accordingly, an annular space between
adjacent seals 66 is formed at each port 60 and 62 to provide
continuous fluid communication of these ports with an external
fluid source during rotation of the carrier 12. Channels 68 and 70
in boss 20 extend from the annular spaces thus created to the
outside of the housing 10 where hydraulic lines 72 and 74
communicate channels 68 and 70, respectively, with a hydraulic pump
76 and a reservoir 78 via a two-way valve 80. Although valve 80 is
diagrammatically illustrated as a simple valve for reversing fluid
flow in the lines 72 and 74, it should be understood that in
practice the valve 80 would be provided with a variable orifice or
other means of controlling fluid flow so that the volume of the
fluid flow, as well as its direction, will be under the control of
the operator.
Likewise, the pinion gear 38 is fixed to the shaft 82 of a
hydraulic motor 84 having a fluid inlet and outlet 86, 88
communicated by respective channels 90, 92 in housing 12 with the
corresponding annular spaces defined by the three seals 66. The
pinion gears 36 and 38 can be driven in either direction, depending
upon the direction of fluid flow as governed by the valve 80. In
either operational condition, the opposing pinion gears 36 and 38
rotate in opposite directions. Accordingly, utilization of the
differential of FIG. 1 in tracked vehicles provides direct control
of the relative speeds of the two output axles for steering
purposes without the need to employ a complex drive or to declutch
and apply a brake to the track on the inside of a turn.
Referring to the embodiment of FIG. 2, the differential-gearing
device there shown is structurally identical to the embodiment of
FIG. 1 except for the substitution of hydraulic pump units 100 and
102 for the hydraulic motors 50 and 84 respectively, and a
modification of the external hydraulic system. Accordingly, the
same reference numerals are utilized in FIG. 2 to designate like
parts and components, with the addition of the "a" notation. The
embodiment of FIG. 2 provides a locking and limited slip
differential for wheeled vehicles where, under adverse traction
conditions, it is desired to have the capability of forcing the
output shafts 22a and 24a to rotate at the same speed or limit the
speed difference therebetween.
The hydraulic pump units 100 and 102 are positive displacement
pumps in which control of fluid flow results in control of the
pinion gear motion. Pump unit 100 has an oil inlet 104 and an
outlet 106 communicating with external hydraulic lines 74a and 72a
which extend to a reservoir 108 via a valve 110 under the control
of the operator. The pinion gear 36a is fixed to the operating
shaft 112 of pump unit 100; likewise, the pinion 38a is fixed to
the operating shaft 114 of pump unit 102. The hydraulic lines 72a
and 74a, via channels 68a, 70a and 90a, 92a, extend to the oil
outlet 118 and inlet 116 of pump unit 102. When the valve 110 is in
the open position illustrated, the pump shafts 112 and 114 (and
hence the pinon gears 36a and 38a) are allowed to rotate freely as
fluid flow to and from the reservoir 108 is unimpeded. In this
mode, therefore, the speed of output shafts 22a and 24a is allowed
to vary independently. However, upon closure of the valve 110,
fluid flow in the hydraulic system is blocked and the hydraulic
pumps 100 and 102 are locked to force the output shafts 22a and 24a
to rotate at the same speed. It may be appreciated that partial
opening of the valve 110 restricts the fluid flow from the pumps
100 and 102 and thus limits the speed variation between the two
output shafts 22a and 24a.
It should be understood that any number of pinion gears may be
employed in the differential assembly of FIG. 2 and in the other
embodiments of FIGS. 1, 3 and 4. In light duty applications it may
not be necessary to control all of the pinion gears, thus some may
be left to rotate freely.
Referring to FIG. 3, this embodiment of the invention provides a
hydraulic clutch for controlling the transmission of rotative
motion from an input shaft 120 to an output shaft 122 coaxially
aligned therewith. Other than right to left reversal and a
modification in the interior configuration of the housing 10b, the
differential-gearing arrangement and control of the pinion gears
are identical to that shown in FIG. 2 except for the arrangement of
the input and output shafts of the device. It may be seen that the
drive pinion and ring gear are omitted and that the input is
supplied by the shaft 120 which has its inner end fixed to the
bevel side gear 32b. The opposing, inner end of the output shaft
122 carries the bevel side gear 34b. Other parts and components
identical to that described or illustrated in FIG. 2 are identified
by the same reference numerals with the addition of the "b"
notation.
External hydraulic lines 124 and 126 communicate with a reservoir
128 via a valve 130, and extend to passages 132 and 134,
respectively, in housing 10b that, in turn, communicate via the
rotating fluid coupling with the oil inlets 104b, 116b and outlets
106b, 118b of the hydraulic pump units 100b and 102b. Each of the
pump units 100b and 102b is a positive displacement piston pump
driven by the corresponding pinion gear 36b or 38b. When the valve
130 is open as illustrated, fluid flows freely between the
reservoir 128 and the pump units 100b and 102b; thus, the pinion
gears 36b and 38b rotate in response to the input shaft 120 and
rotation is not transmitted to the output shaft 122. Closure of the
valve 130 blocks fluid flow and locks the pump units 100b and 102b
to thereby prevent rotation of the pinion gears 36b and 38b and
transmit rotating motion to the output shaft 122.
The embodiment of FIG. 4 employs the principles of the present
invention to provide a variable speed transmission. The
differential gearing arrangement is identical to that illustrated
in FIG. 3, corresponding parts and components being identified by
the same reference numerals with the addition of the "c" notation.
The embodiment of FIG. 4 differs from FIG. 3 in that a variable
displacement hydraulic motor 140 is mounted within the housing 10c
but is separate from the rotatable carrier 12c. The output shaft of
hydraulic motor 140 is connected by spur gears 142 to output shaft
122c, external hydraulic lines 144 and 146 being communicated with
motor 140 via passageways 148 and 150 respectively in housing 10c.
Hydraulic line 144 communicates with a reservoir 152, whereas line
146 communicates with passage 132c via a valve 154 and line 156. A
hydraulic line 158 extends from passage 134c to the reservoir 152.
The transmission is disengaged (drive removed from output shaft
122c) when the valve 154 is shifted to a position communicating
line 156 with reservoir 152, thereby removing the hydraulic motor
140 from the hydraulic system and rendering the pinion gears 36c
and 38c freely rotatable as in FIG. 3 (declutched condition).
OPERATION
The differential with axle speed control of FIG. 1 may be
advantageously utilized to steer a tracked vehicle as previously
discussed. When the input shaft 40 is in motion, the direction of
fluid flow in the hydraulic lines 72 and 74, as governed by the
position of the valve 80, determines which axle or output shaft 22
or 24 has the highest speed. The volume of fluid flow determines
the speed difference between the two axles and, therefore, the rate
at which the turn is executed.
When the input shaft 40 is stopped, as would occur with the drive
disengaged, the output shafts 22 and 24 will turn in opposite
directions as governed by the direction of fluid flow in the lines
72 and 74. Again, the volume of fluid flow will determine the speed
difference between shafts 22 and 24. This enables a tracked vehicle
to turn in place while stopped.
With respect to the locking and limited slip differential provided
by the embodiment of FIG. 2, it may be seen that the substitution
of hydraulic pumps 100 and 102 for the hydraulic motors 50 and 84
utilized in FIG. 1, and modification of the external hydraulic
system, provide a means of locking the output shafts 22a and 24a
under difficult traction conditions such as icy roadways. As the
embodiment of FIG. 2 is primarily intended for wheeled vehicles,
steering is accomplished in the conventional manner. It should be
appreciated that in both the embodiments of FIGS. 1 and 2, as well
as FIGS. 3 and 4, continuous hydraulic connections are effected to
the rotating carrier through the utilization of the seals 66 that
define annular spaces between the stationary and rotating parts of
the device.
The hydraulic clutch of FIG. 3 is engaged by operating the valve
130 to block the fluid flow in the lines 124 and 126, thereby
freezing the piston pumps 100b and 102b to prevent rotation of the
pinions 36b and 38b. The output shaft 122 under such condition is
forced to rotate with the input shaft 120 by virtue of the
interengagement of the pinion gears and the side gears 32b and 34b.
If valve 130 is partially closed rather than fully closed,
restricted fluid flow to and from the reservoir 128 will permit a
degree of rotation of the pinion gears 36b and 38b and thus drive
the output shaft 122 but at a slower speed than the input shaft
120.
In the variable speed transmission of FIG. 4, both the valve 154
and the variable displacement hydraulic motor 140 are under the
control of the operator. The hydraulic motor 140 may, for example,
comprise a piston-type motor having a displacement that is varied
by changing the length of the stroke of the pistons, and would
typically be varied by a hand-control lever (not shown). The
transmission of FIG. 4 operates much in the same manner as the
clutch of FIG. 3 with the addition of the motor 140 which permits
control of the speed of the output shaft 122c and increases
efficiency when the output speed is less than the speed of the
input shaft 120c.
The function of the variable displacement motor 140 is to control
the volume of fluid flow in the hydraulic system that includes the
two pump units 100c and 102c connected to the pinion gears 36c and
38c. At high displacement, which is high fluid flow, the output
speed is lower than the input speed. When the displacement is
reduced to zero, fluid flow stops, the pinion gears are locked and
output speed equals input speed. Accordingly, by varying the
displacement of the motor 140 between zero and maximum, the ratio
of the speed of the output shaft 122c to the speed of the input
shaft 120c is controlled and may be selected as operating
conditions dictate.
* * * * *